Neighbor 19-year-old Michaela Fallon said she lives on Lost Lake Way a few houses away from Harrouff, who is also 19.

"I looked him up on Facebook and we had like 67 mutual friends," said Fallon.

According to Fallon she and Harrouff attended different high schools but said he seemed like any other college kid.

"It's very troubling that we walk our dog past the house and the people that were killed were innocent," said Fallon standing beside her sister, 21-year-old Meghan Fallon, with a dog in tow Tuesday.

"He looks normal like he's in a fraternity at FSU," added Meghan. "He's from Jupiter, he went to Suncoast I don't know what happened if it was crazy drugs or something."

Martin County Sheriff's Office deputies said Monday night Harrouff was having dinner with his family at a Duffy's Restaurant on Indiantown Road in Jupiter when he stormed out, walked to a seemingly random house and attacked.

Investigators said Harrouff killed the couple inside the home on Kokomo Lane and stabbed a neighbor who tried to intervene.

Sheriff William Snyder said when his deputies arrived on scene they found Harrouff biting a victim's face and it required multiple people to subdue him.

Tuesday Snyder said initial drug testing done on Harrouff came back negative but said investigators were digging deeper, working to obtain a warrant to examine Harrouff's hair and blood for drugs that may not show up on first round tests.

"We've been very careful collecting all the evidence at the hospital because really the big unanswered question is why he did this," said Snyder.

This crime is especially disturbing and puzzling to the Fallon sisters when compared to Harrouff's portrayal on social media.

A Facebook account showed pictures of Harrouff in an Alpha Delta Phi fraternity T-shirt, the teen grinning next to a girl on a boat, and more photos of an athletic, accomplished teen that to many seemed so different from the suspect in this gruesome crime.

In an e-mail, the Executive director Alpha Delta Phi fraternity offered an official statement regarding, "the tragic and horrific incident involving Austin Harrouff."

According to the statement:

"...We are working closely with our chapter leaders at Florida State to monitor any developments; we will cooperate fully with law enforcement authorities and with any legal investigation if asked. We extend our deepest sympathy to the families of the victims. We have no further comment on this matter, which was not related to any fraternity event or activity."